As a prior-art bucket-type jaw crusher attached to an arm of a work machine such as a hydraulic excavator and the like, a bucket for crushing and selecting stones in Japanese Patent Laid-Open No. 2009-45529 (Patent Literature 1), for example, discloses a bucket structure provided with an inlet opening portion and an outlet opening portion for a material such as stones, a shovel-shaped main body regulating a flow direction of the material such as the stones between this inlet opening portion and the outlet opening portion, first and second jaws attached in this main body and opposed to each other, moving means having an eccentric connection portion between a member rotationally moving around a rotation axis and the first jaw so as to give first rotational movement and translational movement of the first jaw around the rotation axis in relation at least with the first jaw by bringing the first jaw close to or separating the same away from the second jaw in order to crush the material such as the stones flowing through these jaws, and a toggle connection portion between the main body and the first jaw in order to give second rotational movement and translational movement of the first jaw, in which this toggle connection portion has a support column pivotally supported by the first jaw and the main body so as to rotationally move around the respective pivotal support axis, this support column extends between the first jaw and the main body so that a line segment connecting the both pivotal support axes inclines by an angle larger than 90° with respect to a line segment connecting the pivotal support axis between the support column and the first jaw and the rotational axis, and this bucket includes a lower part in which a cell-shaped structural body is formed and a reinforcing plate attached to the respective side portions of the main body.
Moreover, a bucket-type jaw crusher in Japanese Patent Laid-Open No. 2009-56423 (Patent Literature 2) discloses a structure of a bucket-type jaw crusher to be attached to an arm of a hydraulic excavator in which a fixed jaw is provided on an inner surface on the bottom of the bucket, an upper part is pivotally supported by an eccentric main spindle driven by a hydraulic motor opposite to that, a lower part is supported by a toggle plate, and a material to be crushed can be crushed by a moving jaw in inverted triangular arrangement, in which, in an intermediate portion between the hydraulic motor on one side of the eccentric main spindle and a flywheel on the other side, a counterweight is provided so as to adjust the balance, and while the moving jaw is reciprocally moved so as to press down the material to be crushed from the upper part to the lower part by means of rotation of the eccentric main spindle, the toggle plate is attached to an up grade ahead and the material to be crushed is pressed onto the fixed jaw so that strong and fine crushing can be performed.
In these types of the bucket-type jaw crusher, an eccentric shaft is provided on a shaft portion supporting the moving jaw and this is rotated, and thus, a motion trajectory of the surface of the moving jaw and a jaw plate is close to a circular motion in the vicinity of the eccentric shaft but changes from an oval motion to an arc motion as it gets closer to a toggle support portion on the discharge side, draws in the material to be crushed to the discharge side by rotating the eccentric shaft in the forward direction and pushes it up to the scooping side by rotation in the reverse direction.
Therefore, in a normal crushing work, only forward rotation is made and not in the reverse direction, and only if the material to be crushed is caught by the jaw crusher, the machine is stopped once, the opening of the bucket is displaced downward, and the crusher is rotated in the reverse direction so as to discharge the caught material to be crushed.
In the bucket-type jaw crusher, since the work of scooping up the material to be crushed and crushing it by the bucket and discharging it is repeated, it is necessary to repeat start and stop of the jaw crusher frequently.
In a stationary jaw crusher (compression-type crusher), the jaw crusher is started from a non-load state, while in the case of the bucket-type jaw crusher, it is started in a loaded state in which the material to be crushed is scooped in the bucket as described above.
Thus, when a hard material to be crushed is to be treated, if start-up of the jaw crusher is to be started in a state where the material to be crushed is caught by directing the opening of the bucket upward, the material to be crushed is bitten, and start-up might become impossible.
Thus, in the prior-art bucket crusher, by starting start-up of the jaw crusher in a state where the bucket is in an inclined posture in the middle of the course from scooping the material to be crushed by the bucket to moving with the opening of the bucket completely upward, a degree of being caught of the material to be crushed at the upward crush position is reduced in the crushing treatment, but an operator needs to adjust timing of start-up in accordance with hardness and size of the material to be crushed, and if the timing is wrong, the material to be crushed is caught and the start-up of the jaw crusher might become impossible.
Moreover, since bucket-type jaw crusher in Patent Literature 2 is configured such that the hydraulic motor is directly connected to one side of the eccentric main spindle, the eccentric main spindle becomes an output shaft of the hydraulic motor, and an impact generated when a foreign substance is bitten is directly transmitted to the hydraulic motor. Thus, if a hard metal material or the like contained in the slag during the crushing treatment of the slag is bitten, for example, there is a risk of giving an extremely large impact load to the hydraulic motor, and the machine cannot be applied to the slag treatment.
Furthermore, in the bucket-type crusher, in order to handle weight limitation, the weight reduction of the moving jaw is promoted, but since a tip end of the jaw plate of the moving jaw is hooked by a hook-shaped hook portion formed integrally on a base portion of the moving jaw, if elongation is generated in the jaw plate made of manganese, it cannot be absorbed but a crack or damage occurs in the hook portion, which causes nonconformity that repair of the entire base portion is required.